Motor fuel composition containing silica gel-extracted bright stock



United States Patent MOTOR FUEL COMPOSITION CONTAINING SILICA GEL-EXTRACTED BRIGHT STOCK No Drawing. Application July 31, 1957 Serial No. 675,259

2 Claims. (Cl. 208-17) The present invention relates to improved motor fuels and methods for making them, and more particularly to motor fuels containing additive agents adapted to reduce or prevent gum problems in the motor while simultaneously lubricating the moving parts in the upper part of the motor. More particularly, the present invention relates to a gasoline composition containing an improved solvent oil adapted to prevent valve stem and piston ring sticking and be a general purpose upper cylinder lubri- .cant.

The use of solvent oils in gasoline composition to control these problems and provide upper cylinder lubrication has long been known. Thus, a satisfactory composition is described in US. Patent 2,066,234, issued to Sloane and Wasson on December29, 1936. This patent describes solvent oils as consisting of a liquid hydrocarbon mixture having a 50% distillation point above 350 F. at 10 mm. Hg pressure, having a Saybolt viscosity at 100 F. not above 450 seconds, and having an A.P.I. gravity of about 18 to 28. A typical solvent oil, for

example, has the following inspections:

50% distillation point 413 10 mm. Hg Saybolt viscosity at 100 F. 75.3

In general, the solvent oil is present in a gasoline to the extent of from about 0.05 to 1.0%.

The need for a highly active solvent oil type additive has been long recognized. Manifold deposit and intake valve (particularly underside) deposite buildup represents a serious fuel deficiency, particularly when the fuel is used in low temperature service with considerable engine idling time. Catalytically cracked gasolines which have comparatively high octane numbers and are thus widely used are unstable and require the use of an antioxidant. Both these unstable fuels and antioxidant residues .contribute to manifold and intake valve deposits. Use of a solvent oil type additive represents a desirable method of minimizing these deposits. However, solvent oils of the Sloane-Wasson type, while controlling manifold deposits, are not effective in reducing underside intake valve deposits. The accumulation of these latter deposits under high mileage can cause severe engine operating conditions.

It has now been found that an excellent motor and aviation gasoline solvent oil maybe provided by incorpo- A.P.I. gravity rating in the gasoline, from 0.1 to 1.0% by weight of a bright stock which has been silica gel extracted to an aromatics content of less than about 5%. .Moreparticularly, this invention is based on the surprising discovery that by select silica gel treatment of a deasphalted, solvent extracted, virgin residual oil or bright stock, asolvent oil is obtained that: (l) overcomes ,the problem of intake valve underside deposits to a greater degree than conventional bright stocks and other solvent oils, (2) does not contribute to Octane Requirement Increase (O.R.I.). While it is realized that very high viscosity oils might also be effective, none have been foundwhich would not contribute to O.R.I.

Patented Sept. 15, 1959 Other methods of highly refining bright stocks, such as acid treatment, extensive solvent treatment, or aluminum chloride contacting, do not yield equivalent materials. The reason why silica gel treatment results in such an excellent solvent oil is not clearly understood at this time. -It is postulated that the silica gel is extremely selective to the removal of aromatics and non-hydrocarbons, both of which contribute to instability and Octane Requirement Increase. Further, the remaining hydrocarbons have better solvency for the deposits than the original feed. This is surprising since solvency is normally associated with aromatics, thus indicating that the treatment leaves some materials in the bright stock in the proper amount, i.e., not too much or too little, that ex hibit the desired solvency action in a solvent oil composition.

The silica gel treated bright stock of this invention can be obtained from any convenient crude source. It is much preferred to use as a starting material paraffinic crudes such as North Louisiana and Panhandle. With cmdes other than paraffinic crudes, the treating steps described below result in a substantial loss in yield.

The crude is first treated by simple vacuum distillation to obtain a residual fraction boiling about 950 F. The residual fraction is then at least deasphalted and dewaxed before the silica gel treatment. It is much preferred, however, to also solvent extract the residual fraction before the dewaxing treatment. In some instances the dewaxing step can occur after silica gel treatment, but it is much preferred to carry this out before silica gel treatment and after the deasphalting and solvent extraction steps.

The residual fraction obtained by vacuum distillation is first treated by-deasphalting. Any conventional means of deasphalting can be used. It is preferred to treat the residual fraction with light parafiins such as propane and butane, or mixtures thereof, at temperatures inthe range of 100 to 160 F. and at solvent/oil ratiosin the range of 400 to 1200%. The residual fraction is treated to obtain a material havinga viscosity at 210 F. in the range of ,200-to 250 8.8.11, and a Conradson carboncontent of less than 1 wt. :percent. For the preferred paraflinic residual fractions, the yields arein the range of 40 to 70 .wt. percent.

,In .a Preferred embodiment, the deasphalted fraction is;then subjectedto solventextraction employing any conventional solvent such as phenol, furfural, sulfur dioxide, ammonia, nitrobenzene, etc. The extent of the solvent extraction is such as to obtain a material having a V1. above 100, which reflects the reduction in aromatic content, and a viscosity in the range of 100 to 150 S. S.U. at 2105B. The yields are in the rangeof 50 to wt. percent ;based on feed to the extraction step.

In thevdewaxing step, the deasphalted residual fraction, -,which-is also preferably solvent extracted as indicated above, is treated to remove the p-arafiins and to lower its pour point to at least below +30 F. The yield obtained depends upon the wax content of the fraction and is-usually in the range of 70 to for p-arafiinic type residual oils. Conventional dewaxing techniques can be used, solvent dewaxing being preferred. In this method, the residual fraction is contacted with about 2 to 4 parts per volume with a solvent such as propane or methyl-ethyl-ketone. The mixture is then heated to assure solution of the wax, andis then chilled to about 25 to -10 F. to obtain crystallization. The mixture isthenfiltered or.cent-rifuged,to remove the Wax.

The-bright stock so obtained by the deasphalting and dewaxing steps may then be further treatedas desired, such as by decolorizing, as by clay cont acting, although this isnot necessarybecausethe silica ,gel treatment accomplishes about the same results.

The bright stock is then treated specifically with silica gel to obtain the desired material to add to gasoline compositions. As discussed later (Table IV), other methods of highly refining residual fractions would not give equivalent results; The silica gel treatment is well known in the art and is carried out in a conventional manner by percolating the bright stock, preferably in solution with a solvent such as heptane, through a column of silica gel. A preferred silica gel is the standard commercial 28/200 mesh manufactured by the Davison Chemical Company. It is preferred to contact the bright stock with 300 to 1600 wt. percent of the silica gel at a temperature in the range of 50 to 100 F. The silica gel can be periodically regenerated as desired by standard solvent elution, as for example, with acetone, benzene, Cellosolve, or mixtures thereof. The silica gel treatment is sufiicient to reduce the concentration of single ring aromatics to below 5 wt. percent and to reduce the condensed ring aromatics to essentially negligible proportions, i.e., less than 0.01 wt. percent. By single ring aromatics are meant compounds containing a single benzene nucleus, and by condensed ring aromatics are meant compounds such as anthracene and derivatives thereof, both as determined by spectographic analysis.

The following Table I gives the inspections of the final silica gel treated virgin bright stock that must be met in order to obtain the suitable solvent oil of this invention.

TABLE I Viscosity at 210 F., SSU 70 to 150. Viscosity index 100 to 120. Conradson carbon, wt. percent Below 0.1.

Single ring aromatics, wt. percent Below 5. Condensed ring aromatics, wt. percent Nil. Pour point, F. Below +30. Gravity, API 27 to 32. Tag. Robinson color Above 15. Nitrogen, wt. percent Nil. Sulfur, wt. percent to .05. Initial boiling point Above 850 F. R1. (Resinification Index) Below 16 mg./ gr.

described solvent oil is either added to the gasoline itself or is injected into the manifold in any desired manner in order to contact the gum-coated surface. The amount of solvent oil to be used may vary over a wide range depending upon various factors such as the type of motor fuel being used and the type of engine. In general, from Gravity, API 31.1. Viscosity, SSU {g; ig9 Conradson carbon 0.01. Aromatics 3.0%.

R.I. 67 C. 1.4598.

Sulfur 0.03%. Nitrogen (comb) Nil.

The chief property examined was the relative ability of the solvent oils to keep the underside of the intake valve clean. A completely clean valve would give a O demerit rating and a completely fouled valve would give a 10 demerit rating. In addition, its contribution to combustion chamber deposits and its effect on octane requirement increase (O.R.I.) were measured.

TABLE 11 COMPARISON OF SOLVENT OILS [In high octane premium gasoline and using a 10 W30 lubricating oil in a dual fuel system Buick, run about 6,500 miles] Solvent oil (vol. percent) Demerit Comments Coongentional solvent oil B 2.5 Some spark plug fouling. L Solv eni. oil A (0.5%) 0.75 No spark plug fouling.

Silica gel treated bright 0.75 No spark plug fouling. stock (0.25%). Very slight surface igni- 'tion (not; limiting in any way). Conventional naphthenic 0. 5 to 0. 7 Very severe spark plug bright stock (0.5%). fouling.

TABLE III 0.05 to 1.0% of solvent oil is sufficient, and preferably the amount used is between 0.10 to 0.75% by volume based on the gasoline blend.

The solvent oil composition of the present invention is also applicable to dissolving and fluxing gummy deposits from such fuel systems as diesel, heating oil, jet engines, turbines and the like. Furthermore, it may be combined with additives in motor fuels having other properties, such as dimethyl carbinol for de-icing, various anti-rust agents and the like.

Example 1 A bright stock prepared in the manner previously described was tested as a solvent oil in a high octane premium gasoline. centration in a duel fuel system Buick engine operating with premium gasoline and a 10 W-30 lubricant. The

The sample was tested in 0.25% con- I DUAL FUEL SYSTEM BUICK Oil: 10 W-30 Fuel: Premium gasoline Solvent oil Silica gel treated bright Solvent stock oil A" Solvent oil concentration, percent 0.25 0, 5 Tank Left Right Carburetor deposits (grams): Heptane soluble 0.15 0, 08 Acetone soluble 0. 05 0, 03

Total 0 20 n Manifold deposits (grams):

Heptane soluble 0. 39 0. 81 Acetone soluble- 1. 19 0. 06

Total 1 58 0. s7

Combustion chamber deposits (grams) 31. 44. 66 Demerit ratings: Piston top 1. 5 1. fi3 1. 0 1. 25 1.25 1. 50 2. l3 1. 63 1 0.69 0. 05 0.31 0.31 1. 50 1. 13 Exhaust valve stem 1, 31 1, 31 Octane requirements: 'Prim. ref. fuels' 1 Very slight surface ignition.

The data in Table II show that the use of 0.25 Volume percent of silica gel bright stock in the premium gasoline was effective in reducing intake valve underside deposits in the test car, and does so in a manner superior over commercially available solvent oils. In half the concentration, the oil of the present invention did a better cleaning job than the commercially available solvent oil B. Furthermore, when a conventional bright stock, which is high in naphthenic content is employed as a solvent oil, spark plug fouling was observed, whereas the silica gel extract material did not show any spark plug fouling. It is also well known that conventional bright stocks contribute to O.R.I. As shown in Table III, the present invention (silica gel extracted bright stock) does not contribute to O.R.I.

Table III shows in detail the advantages of incorporating into a gasoline the silica gel treated bright stock over solvent oil A, which has hitherto been considered to be the most desirable type of solvent oil. In fact, solvent oil A is normally used as a target for commercial solvent oils but because of its high cost is not used commercially. The solvent oil of the present invention is substantially superior over the target.

For example, total combustion chamber deposits are lower for the silica gel treated bright stock than for solvent oil A (31.8 vs. 44.6). Furthermore, the Octane Requirement Increase is about 50% less than using the silica gel extracted bright stock.

Table IV gives a comparison of the properties of several highly refined bright stocks. A screening test to evaluate the tendency of these oils to contribute to Octane Requirement Increase is the Hydrogen Combustion Test which determines the Resinification Index referred to in Table 1, page 7. The test is described in detail in US. Patent 2,761,766, issued September 4, 1956 to A. H. Popkin. Basically, 5 grams of oil (straight or in blend with another oil) are burned under specified conditions in a hydrogen flame until a dry residue remains. The weight of deposits for a given weight of charge defines the Resinification Index.

As shown in Table IV, the silica gel treated bright stock is superior to the other types of super refined bright stocks since it has the lowest resinification Index.

The phenol treated material in Column 2, Table IV, was obtained by further extracting a conventional bright stock with 300% anhydrous phenol at 200 F. in a single stage batch treat. The rafiinate was stripped of phenol to a 78% yield.

TABLE IV EFFECT OF BRIGHT STOCK REFINING ON OCTANE REQUIREMENT INCREASE TENDENOY Oonven tional refining plus Process Phenol extraction AlCla Alu- Silica W/ mina ge 1 Clay clay Yield, vol. percent-- 100 78 80 98 96 70 Gravity, API 28, 5 26, 7 Viscosity, SSU:

At 100 F 1, 126 2, 068

At 210 F 100. 2 141 95 Viscosity index.---- 101 105 104 101 108 104 2, weight percent.-

S weight percent--- donradson carbon,

0. 26 0. 75 Resinification index Straight 1 49 54 21 29 47 12 5% in a distillate motor oil 11 13 9 7 9 5 weight. percent.--

Average 01 at least two determinations.

The material in column 3 was obtained by treating with 5% of aluminum chloride for two hours at 350 F. followed by clay treating.

The clay treated oil in column 4 was obtained by contacting the oil with Superfiltrol clay at 400 to 450 F. for one hour. Treat was one-half pound clay per gallon of oil. The alumina treated oils were obtained in a conventional manner by percolating the bright stock in heptane solution through Alcoa F-20 alumina at room temperature to a 96% yield.

An attempt was made to severely acid treat the bright stock with sulfuric acid. It was not possible to acid treat the heavy conventional bright stock to a reasonable yield level and produce a material even worthy of testing.

What is claimed is:

1. A fuel composition comprising light hydrocarbons boiling in the gasoline range and 0.1 to 1.0% by weight of a silica gel extracted bright stock having less than 5% aromatics content and a pour point less than +30 2. The composition of claim 1 wherein said bright stock is derived from a paraflinic crude by first distilling the crude to obtain the residual fraction, deasphalting said residual fraction to obtain a material having a viscosity at 210 F. in the range of 200 to 250 SSU and a Conradson carbon content of less than 1 Wt. percent, extracting the deasphalted material with a solvent to obtain a material having a viscosity index above 100 and a viscosity in the range of 100 to SSU at 210 F., dewaxing the solvent extracted material to a pour point below +30 F., and treating the dewaxed material with 300 to 1600 wt. percent of silica gel to obtain said bright stock having the following characteristics:

Condensed ring aromatics, weight percent Nil.

References Cited in the file of this patent UNITED STATES PATENTS 2,654,697 Andress et a1. Oct. 6, 1953 

1. A FUEL COMPOSITION COMPRISING LIGHT HYDROCARBONS BOILING IN THE GASOLINE RANGE AND 0.1 TO 1.0% BY WEIGHT OF A SILICA GEL EXTRACTED BRIGHT STOCK HAVING LESS THAN 5% AROMATICS CONTENT AND A POUR POINT LESS THAN +30* F. 